Cover hold-down clamp for screening machines



A. c. NOLTE 3,433,357

DOWN CLAMP FOR SCREENING MACHINES March 18, 1969 COVER HOLD- Sheet of 2 Filed Jan. 5, 1967 ATTQRNEYS.

A. c. NOLTE 3,433,357

COVER HOLD-DOWN CLAMP FOR SCREENING MACHINES March 18, 1969 Sheet Filed Jan. 5, 19 7 ATTORNEYS United States 3,433,357 COVER HOLD-DOWN CLAMP FOR SCREENWG MACHINES Arthur C. Nolte, Cincinnati, Chic, assignor to The Orville Simpson Company, Cincinnati, Ohio, a corporation of Ohio Filed Jan. 3, 1967, Ser. No. 606,886 U.S. Cl. 209-372 Int. Cl. B07b 1/28 Claims ABSTRACT OF THE DISCLOSURE This invention relates to clamping devices for use with machinery of the type used to sift, screen, size or separate particulate material, which machines are generically referred to herein as screening machines.

In such machines one or more screens are mounted in sloping planes within a screen frame, or screen box, and the material to be separated is discharged onto the screens. A vibratory motion imparted to each screen shakes the material permitting the finer particles to fall through the screen openings while the coarser materials remain on top of the screen. Such machines are commonly provided with a top cover which encloses the screen assembly, and this top cover is clamped to the screen frame or screen box around the screens. More specifically, this invention relates to an improved clamping mechanism especially suitable for such use.

Various clamping mechanisms have been provided in the past for holding the top cover to the screen frame, but they have been subject to non-uniform operation at different adjustments. For example, the clamp movement required to achieve a desired hold-down force has varied with slight top cover misalignment, and with screen thickness, and this has often resulted in non-uniform clamping, and even different throw or movement from clamp to clamp on a given machine.

In many previous arrangements, the clamp has simply been a bell crank on a threaded rod engaged between the top cover and frame; the crank is turned to bring the top cover down progressively. Such cranks of course do not necessarily provide uniform clamping along the length of the top cover, and their operation is a relatively slow procedure since several clamps are ordinarily required on each screening machine. In other instances, where clamps of the over-center type have been used, the amount of throw, and hence the clamping force, varies with the cover alignment, so that different clamping pressures may [result from minor differences in cover position. Bearing in mind that a standard screening machine may be used with screens having thicknesses, say, from inch bolt cloth, up to heavy /2 inch thick wire screen, and also that the total screen thickness depends upon the number of screens mounted in the machine which can also be varied, the importance of clamping flexibility, coupled with consistency of operation, can be appreciated.

The clamp of the present invention is of the overcenter type, and includes a toggle portion, a portion pivotally connecting the toggle to the screen box for rotary movement about a first axis parallel to the general plane atent G of the screen frame, and an operating handle pivotally connected to the toggle at the end thereof remote from the first axis for swinging movement toward the first axis. A pair of pins or studs project from the handle, and these pins are engageable in seats presented on the top cover. When the pins are engaged in the seats, swinging the handle about the toggle brings the pivotal connection of the handle to the toggle from a point lying on one side of an extension of a line drawn between the first axis and the pins, to a stable clamping position on the opposite side of that line. Stops on the toggle limit the motion of the handle once it has crossed top dead center, to a pm sition which is constant regardless of the relationship of the handle to the top cover. When the handle has been thrown, the toggle is nested within the handle in a compact, enclosed relation.

The invention can best be further described by reference to the accompanying drawings, in which:

FIGURE 1 is a perspective view showing one illustrative type of commercial screening machine with which the clamps of the present invention are suitable for use;

FIGURE 2 is a front elevation of a portion of the screen box and top cover of a screening machine such as that shown in FIGURE 1, showing a clamp embodying a preferred form of the invention, with the handle in raised or open position;

FIGURE 3 is a side view, partly in section, showing the handle as the pins thereon are about to be engaged with the top cover to pull the latter down upon the screen frame;

FIGURE 4 is a side elevation similar to FIGURE 3, but shows the handle in clamping position and holding the top cover down on the screen frame; and

FIGURE 5 is an enlarged front elevation, partly broken away, particularly illustrating the toggle, handle and bolt interconnecting means.

The clamping mechanism of this invention is typically utilized with screening machines which may be of the type shown in FIGURE 1 for purposes of illustration. Such machines may be as much as fifteen feet long, and may weigh several tons. The machine includes a base 11 and a screen box 12 within which may be mounted one or more parallel screens of graduated mesh sizes, one screen being showin in FIGURE 5. At its lower end, screen box 12 rests on slide pads, one of which is designated at 13. At its upper end or head, the screen box is driven by an electric motor 14 through an eccentric or other screening motion-creating means 15 which imparts an oscillatory, gyratory, o-r rotary motion to the screen box head.

Screen box 12 has a top cover 17 which completely encloses the screens within it, to prevent the material being screened from contamination by extraneous matter, and to minimize the escape of dust and fines from the box. A gasket or other seal, such as that described more fully hereinafter, may be provided between the top cover 17 and the box 12.

Top cover 17 is removably clamped with respect to the screen box 12 by a plurality of hold-down clamps in accordance with the invention, each designated generally by 21. The material to be screened is charged onto the upper end of the screen in screen box 12 through a chute 22 which passes through a port or opening in top cover 17. As is well known, when the machine is operated, the particulate material entering through chute 22 moves generally in the downward direction along the length of the screen in the box, the finer materials pass through the screen while the tailings pass off the lower end of the screen into separate collecting means.

One of the clamps 21 is shown in detail in FIGURES 2, 3 and 4, in association with the top cover and screen box assembly. The top cover 17 shown has a side portion which includes an extruded member 26 having a pair of branches, one of which comprises a dust guard 27 and the other of which, designated at 28, receives a rubber seal strip 29 which bears on the screen periphery.

The screeen box 12 has a planar upper edge 31 and is fitted with a liner 32 having a lip or rim 35 which is straddled by the top cover branches 27 and 28. The screen 34 is stretched tautly across a screen frame 33 by a plurality of tensioner springs 36 (see FIGURE 4).

In the particular screening machine shown for purposes of illustration, to top cover 17 is clamped with respect to the box 12 by placing the rubber seal 29 in compression between the top cover branch 28 and the screen itself.

Alternatively, in some instances, the top cover may be clamped to the screen frame, or to the screen box, rather than onto the screen itself as here shown, and it will be understood that in the claims which follow, the language clamping the top cover over said screen in fixed position with respect to said frame is intended to include these various modes.

The screen frame 33 has a rubber seal or compression strip 37 along its lower edge which bears upon the screen box liner 32 as here shown or, where a plurality of screens are enclosed within the box, upon the next lower screen.

The clamp 21 comprises three main components, a toggle portion 41, a connecting member 42 through which the toggle 41 is adjustably connected to the screen box 12, and an operating handle 43. The toggle 41, as seen in FIGURE 5, preferably is a casting having a base portion '46, a head portion 47, and legs 48 and 49 extending between and joining the head and base.

The connecting member 42 preferably comprises a bolt which is threaded at one end into a longitudinal bore 51 in the base of the toggle, and which is adjustably locked with respect thereto by a lock nut 52. As shown in FIG- URES 2 and bolt 42 passes transversely through a transverse opening in a pivot, bar or articulating means 54, and the bolt head 53 bears against the bar. The ends of the bar 54 are journalled in holes formed in a U-shaped bracket or channel 56 which is welded or otherwise secured in desired position on the surface 31 of screen box 12. Spring clips 57, 57 snap into grooves (not shown) in bar 54 and prevent longitudinal displacement of the bar in channel 56.

The operating handle 43 is an elongate member which preferably is of U-shaped cross-section, having a web 61 and limbs 62, 63. The internal spacing between limbs 62, 63 should preferably slightly exceed the width of toggle 41, that is, the outside dimension acrossthe toggle legs 48, 49, so that in the closed position shown in FIG- URE 4 the handle will :fit closely over and cover the toggle. Preferably the limbs 62, 63 of the handle are narrowed toward the outer end of the handle, as at 64, in order to provide clearance between the limbs 62, 63 and bar channel 56.

Adjacent its opposite end 66, handle 43 is connected to the head 47 of toggle 41 by a pivot 67 extending between the limbs of the handle. Fixed close to but offset from the axis 68 of pivot 67 is an axle defined by a pair of stub pins 70, 71 which project outwardly from the respective limbs 62, 63 of handle 43. These stub pins 70, 71 acts as an axle and are engageable with semi-circular recesses, bearing means, or seats, one of which is shown at 72 in FIGURE 3, formed in a clamp latch or bracket 73 welded to the top cover 17. This latch 73 may suitably comprise a casting having a pair of spaced ledges 74, 75 with a recess or space 76 between them of sufficient width to accommodate the width of the handle 43.

In the operation of the clamp, when the top cover is seated on the screen and toggle head 47 is positioned in the space 76 between the clamp latch edges 74, 75 as shown in FIGURES 2 and 3, it will be seen that swinging the handle 43 about the pivot axis 68 will bring the stub pins 70, 71 into engagement with their respective seats 72. When the stub pins 70, 71 are seated, the center line or axis 68 of pivot 67 will be on one side (the right side in the drawings) of the extension of a line 69 drawn between the axis 77 of bar 54, and the axis 78 of pins 70, 71. Since the dimension between axes 77 and 68 is fixed, as the handle 43 is swung downwardly toward axis 77, the stub pins 70, 7-1 bear with increasing force against the latch 73 and thereby urge the top cover down onto the screen. Such swinging movement of handle 43 toward axis 77 moves pivot axis 68 over-center, that is, from the right side of the above described line 69, to the left side, as shown in FIGURE 4. When the handle is moved sufficiently across center to reside in a stable position, its movement toward the screen box is arrested by a pair of stops 80 and 81 which project outwardly from toggle 41 adjacent the base 46 thereof. These stops 80 and 81 are of sufficient dimension to intercept movement of the respective limbs 62, 63 of handle 43 (see FIGURE 5).

The threaded engagement of connecting member 42 with toggle 41 permits the effective length of the clamp to be varied to accommodate screens of a range of various thicknesses, different top cover dimensions, and different top cover positions. This is done simply by loosening lock nut 52 and turning toggle 41 relative to bolt 42, until the handle stub pins 70, 71 are positioned for proper clamping engagement with the latch seats 72. Lock nut 52 holds the desired position.

I have found that the positioning of stops 80, 81 on the toggle is particularly effective in providing more uniform clamping operation with changing clamp lengths and with different cover alignments on the frame. These stops limit the over-center movement of the clamp handle at a certain angle with respect to the toggle, rather than limiting its movement at a certain position with respect to the screen frame. Thus the throw, or over-center travel of the handle, does not depend on top cover position or dimension, but only on clamp construction, which is constant. Were stops provided on the screen box for example, or on the top cover, different throws would result with different cover positions and the clamping force would be irregular from clamp to clamp and use to use.

It can also be seen that the clamp is placed in tension by the force of clamping; that is, the force between axes 68 and 78 acts along the longitudinal axis of the toggle and connecting member 42. Thus these elements are subject to less distortion than previous clamps of the C-type, which have been subjected to bending stresses.

While I have described a preferred form of my invention herein, those skilled in the art will recognize that other forms of clamping mechanism embodying the spirit and principles of this'invention can readily be made in light of the foregoing description, within the scope of the following claims.

I claim:

1. In a screening machine having a screen, a frame supporting the screen, and a top cover for the screen; mechanism for releasably clamping the top cover over said screen in fixed posit-ion with respect to the said frame,

said mechanism comprising,

a toggle having a base, a head, and means joining said head and base,

connecting means extending from the base of said toggle and connecting said toggle to said frame for rotation about a first axis parallel to the general plane of said frame, said connecting means providing for adjustment of the spacing between said first axis and said toggle,

an operating handle rotatably connected at one end by a pivot to the head of said toggle for clamping movement toward the base of said toggle, said handle having a web and spaced limbs configured to nest said toggle between them when said handle is in closed position.

stop means on said toggle limit-ing said clamping movement of said handle toward said base,

a pair of stub pins projecting from said handle, said pins defining a second axis parallel to said pivot, said stub pins being engageable in seats formed on said top cover,

said pivot being positioned with respect to said second axis so that when said when pins are engaged in said seats said pins are between said pivot and first axis and so that said pivot is brought from one side of a line intersecting said axes to the other side of said line when said handle is swung about said pins toward said base,

said stop means being positioned for engagement with said limbs to arrest said clamping movement of said handle beyond that necessary to bring said pivot across said line to a stable position.

2. The mechanism of claim 1 wherein said toggle resides between said limbs closely adjacent the web of said handle when said stop means limits said clamping movement.

3. The mechanism of claim 2 wherein said stop means comprise at least one pin projecting from the base of said toggle and disposed to arrest at least one of said limbs.

4. The mechanism of claim 1 wherein said seats on the top cover are presented by a bracket mounted to the top cover having a pair of ledges spaced sufficiently to accommodate said handle and toggle,

said ledges having recesses defining the seats in which said stub pins can be engaged.

5. In a screening machine having a screen, a frame supporting the screen, and a top cover for the screen; mechanism for releasably clamping the top cover over said screen in fixed position with respect to the said frame,

said mechanism comprising,

a toggle having a base, a head, and means joining said head and base,

connecting means extending from the base of said toggle,

an operating handle comprising a U-shaped channel having spaced side limbs connected by a pivot to the head of said toggle at a point remote from said base for swinging movement toward the base of said toggle, said handle including an elongate gripping portion diverging angularly away from said toggle when in clamping position,

stop means on said toggle positioned for engagement with said limbs limiting said swinging movement of said handle toward said base,

an axle projecting from said handle,

articulating means connecting said connecting means to said frame,

bearing means connecting said axle to said top cover, one of said articulating means and bearing means being disengageable from the respective frame and top cover, said toggle being connectable between said top cover and frame by said articulating means and bearing means,

means for varying the dimension of said mechanism between said articulating means and axle,

said pivot being so positioned with respect to said axle that when said axle is engaged in said bearing means said axle lies between said pivot and said articulating means and so that said pivot is brought from one side of a line intersecting said axle and said articulating means to the other side of said line when said handle is swung about said axle toward said base,

said stop means being positioned on said toggle to arrest said swinging movement of said handle beyond that necessary to bring said pivot across said line to a stable position.

References Cited UNITED STATES PATENTS 1,827,319 10/ 1931 Komenak. 2,114,406 4/1938 Simpson 209408 X 2,901,279 8/ 1959 MacNaught 292-256.5 3,349,581 10/1'967 Quinn 220 FOREIGN PATENTS 722,536 12/ 1931 France.

FRANK W. L'UTTER, Primary Examiner.

US. Cl. X.R. 

